Grinding machine



June 26, 1 w. e. BALDENHOFER GRINDING MACHINE Filed Sept. 19, 1941 5Sheets-Sheet 1 Gttornegs June 1945- W'. G. BALDENHOFER GRINDING MACHINEJune 1945- w. s. BALDENHOFER 2,373,903

GRINDING MACHINE lnvcntor y- ML.-

(Ittorucgs J1me 1945- w. e. BALDENHOFER 7 GRINDING MACHINE Filed Sept.19. 1941 5 Sheets-Sheet 4 Inventor flii? v 0 1M, (Iltornegs June 26,1945.

w. G. BALDENHOFER GRINDING MACHINE Filed s t. 19. 1941 5 Sheets-Sheet 5m d p Snnegtor attorney Patented June 26, 1945 UNITED STATES PATENTOFFICE GRINDING MACHINE William G. Baldenholer, Springfield, Ohio, as=signor to The Thompson Grinder Company, Springfield, Ohio, a corporationof Ohio Application September 19, 1941, Serial No. 411,529

22 Claims.

This invention relates to improvements in surface grinding machines, itmore particularly relating to improving a grinding machine of the typeshown and described in my Patent No.

reversing dogs. After re-loading, the workholder must again be manuallyreturned to the vicinity of the grinding wheel and the control elementsreadjusted for the normal grinding 2,068,529, dated January 19, 1937,having a toolstroke. head slidably mounted on a vertically disposed Inthe machine of the present application decolumn, the tool-head carryinga grinding wheel vices are provided by means of which the aboveand beingcapable of making successive intermitmentioned steps are carried outautomatically. tent traversing feeding movements across a work- The newmachine may, therefore, be considered piece carried on a reciprocatingwork-holder, in as extending the convenience and advantages whichmachine in grinding the tool-head i lowof the machine of the patentreferred to. ered manually to grind stock from the work- One of theobjects of the present invention is piece, whereby certain manualoperations oi that to provide that in the automatic grinding cy patentare automatically performed. when started the grinding wheel isautomatically In the present application, a machine such as lowered inwhat is known as the down-feeding that of said patent may be consideredas one portion of the cy The total amount of down" form of aconstruction to which the invention in feeding is variable by adjustmentto suit difl'erany or all of its parts may be added to the end entworking conditions, with a provision for adthat the convenience andadvantages in operaj t y securing Variation in the Extent of an tlon ofthe machine of that patent are augindividual down-feeding increment. Thedownmented. The invention tends toward a much feeding is maintained atthese set regular incregreater ease of operation in that the grindingments until the desired low point the tool-head is ycle is practicallyautomatic in character, to reach is attained, when further down-feedingwhereby acceptable work is produced by operais arrestedtors of limitedexperience. The fore part of the 95 Another object is the provision ofmechanism following specifications up to the point of brlngwhereby apart of the automatic grinding cycle ing in the new added elements issimilar to the known as the smoothing or "spark-out period descriptionfound in the patent mentioned, and follows in rotation when down-feedingis arthe reference characters employed in this fore rested. Thisspark-out" period is a surfacing part are, as far as possible, the sameas those 80 operation continued for a regulatable length of used in theabovementioned patent for equivatime with the tool-head held at the lowpo t i lent elements. reached when down-feeding ceased. This ope oleSetting out the objects and advant eration is advantageous since thesurfaces of the of the present invention, a brief explanation willwork-pi are f n uneven. and as s usual be made oi the manner in whichthe machine of in surfacing machines, th d g w l f the patent isoperated. With this machine, a lows the irregularities to a limitedextent. In work-piece is placed in position, th height or sparking-out,the decrease in the volume of the grinding wheel is adjusted, t m- 1sparks coming from a stationarily held wheel (so verse dogs ar adjusted,th reciprocatjon r t far as elevation is concerned) shows that onlywork-table and the cross-feeding of the tool-head the high P s are beingaround away Without are started, while th operator manually lowersproportionate increase in the depths of adiacent the grinding wheel fromtime to time a th lower portions. The duration of time allowed for wheelremoves stock from the work-piece. When the spark-Out p i is easilyvaried in h p the surface is finished, the grinding wheel is mannmachine y a simpl a J i-ment. lially elevated to the former height, anda new Another object is to provide means whereby work-piece is loaded inposition. To lessen the when the work-holder reaches the loadingposihazard to the operator, re-loading is preferably tion, the tool-headis automatically elevated to made with the work-holder removed to apoint its former height, this elevation being made with remote from thegrinding wheel, which is seldom a degree of exactness such that in massproducshut down once it has been started. and if artlon schedules, wherethe raw material is of relarangements were made in the machine of thetlvely uniform thicknesses, it is possible to start patent for a loadingposition. it is usually the the next grinding cycle on the nextwork-piece case that the work-holder is moved'to this posiwith noadjustments other than such as are nection only by the manual shiftingor changing of essary to compensate for the natural wearing some of thecontrol elements such as work-holder 66 down or the grinding wheel.

However, it should be explained that another object is to provide thatwith the work-holder moved onto the loading position, this member isretained in this position for the length of time the operator maydesire, and that to re-start the machine on a succeeding automaticgrinding cycle, the operator has only to open a push-button switch.

Anothe object is to provide means whereby, should it be preferred thatthe present machine be operated as the simpler type of theaforementioned patent, which may be advisable when work-pieces differingin character are routed to the machine, such operation is obtainable bythe opening of a switch in the electro-hydraulic control system of thepresent machine.

Other objects will appear from the accompanying specification andclaims.

In th accompanying drawings:

Fig. l is a front elevation of a machine embodying the improvements.

Fig. 2 is a view partly in side elevation and partly in longitudinalsection, on a larger scale than Fig. 1. the sectional portions beingtaken on the line 1-2 of Fig. 1.

Fig. 3 is an enlarged fragmentary horizontal section on the line 3-4 ofFig. 2.

Fig. 4 is an enlarged fragmentary elevation of a portion of theinvention, 1. e., a switch actuating mechanism seen in elevation in Fig.1.

Fig. 5 is an enlarged vertical section on the line 5-5 of Fig. 2.

Fig. 6 is a fragmentary view similar to Fig. 5 but with some of theparts of that figure shown in a different working position.

Fig. 'l is a fragmentary horizontal section on the line 1-4 of Fig. 5.

Fig. 8 is a diagrammatic showing of the devices by which the novelfeatures of the invention are obtained, together with a showing of thehydraulic and electric circuits pertaining to the invention, with someof the parts being shown in longitudinal section and other parts inelevation.

Fig. 9 is an enlarged detail showing a modification of the means forarresting the down-feed of the tool-support, the view being a frontelevation of a portion of the hand wheel, partly broken away which isassociated with the mechanism which operates the tool slide, and ofparts associated therewith which control the extent of the down-feed ofthe tool-support.

Fig. 10 is a top plan of Fig. 9 with some of the parts shown inlongitudinal section, some of the sectional parts being on the lineIl-Ill of Fig. 9.

Fig. 11 is a detail view partly in side elevation and partly inlongitudinal section showing in full and dotted lines three difl'erentpositions of the switch operating lever.

Fig. 12 is a front elevation of a detail to show some of the parts in adifferent position than that illustrated in Fig. 9.

Fig. 13 is a atic view of the switch and its circuits and the partswhich operate the switch, some of the parts being broken away.

Referring to the drawings, the base of the grinding machine is indicatedat I. On this is mounted for reciprocatory motion on a V-way 2 and afiat-way I a work-holder I to which the work W may be attached by any ofthe usual methods.

Reciprocatory motion is imparted to the workhoider by means of fluidpressure acting in a fluid motor. This motor comprises a cylinder I, oneend of which is secured to the inside upper portion of the base I (Fig.l), a piston 8 (Fig. B) and a piston rod I, the outer end of which issecured to a downwardly-extending arm I attached to an extension of thework-holder l (Fig. 1) Fluid under pressure is admitted alternately toeach end of the cylinder 5, there being a port 9 at the right, and aport II at the left of the cylinder 5 (left center Fig. 8).Communicating with these ports are conduits II and II, respectively,which lead to ports in the body portion l3 of the unitary structurehousing the hydraulic valve control mechanism.

' The work-holder is reversed at the ends of a desired stroke by thereciprocatory movements of a master piston valve to which motion isimparted by means of fluid pressure under the control of a piston pilotvalve, which in turn receives its motion from the work-holder itself.Due to the small size of the pilot valve and although the pilot valveoperates in fluid pressure equal to those pressures which the mastervalve controls, the movements of the work-holder are not affected.

' The pilot valve is moved by contact of stopdogs ll and I5 (Figs. 1 and8), adjustably positioned on the work-holder, with lugs l6 and i1integrally attached on the forward and rear side of a reversing leverit, which is pivotally mounted, on the forward side of the base i, onthe shaft it The shaft l9 extends into the interior of the base i and onits inner end there is secured a. forked lever 11, Fig. 8, whichstraddles the extended stem 23' of the pilot valve 23 between thecollars 23" on this stem. The pilot valve 28 is a portion of thehydraulic valve control mechanism which will be described later in thespeciflcations.

The abrasive wheel 24 (Figs. 1 and 2) is mounted on the end of thehorizontal shaft or spindle 25 supported in bearings (not shown) carriedby the tool-holder or slide 28. The tool-holder is supported inangularly disposed ways I! machined in the lower part of a projectingportion 30 of a vertical support or slide Ii. The support or slide Si isgibbed by gibs 82 to the vertically disposed ways 13' of a column llattached to the base I, and by means of a grinding wheel elevationmechanism may be elevated or lowered so that the position of the wheel24 with respect to the work on the work-holder 0 may be altered.

The grinding wheel elevating and lowering mechanism comprises anelevating screw 2|, Figs. 1 and 2, depending from bearings in the upperend of the column 33. The screw is threaded through a nut 20' secured tothe column side of the vertical support or slide II, and at its lowerend there is secured the gear 2i (Fig. 2) meshing with a pinion II. Thepinion II is secured on the inner end of an elevation cross-shaft 22rotatably carried in hearings in the base. The cross-shaft extendsforwardly throuflh the forward wail of the base, and on its outer end isfixed a hand wheel 22'. On the portion of the cross-shaft 22 justoutside the base there are attached certain members of the devices bywhich the automatic elevation and lowering of the grinding wheel isprovided, the parts being contained in a housing interposed between theforward wall of the base I and the hand wheel It. A full description ofthese new parts will appear in a latter portion of the specification.Rotation of the hand wheel 22' and cross-shaft 22 in an anti-clock-wisedirection as viewed in Fla. 1 results in a lowering of the support orslide 3| and of the holder IO and grinding wheel carried thereby, whilethe reverse rotation elevates the parts.

The tool-holder or slide 28 is actuated by a fluid motor similar to themotor previously described in connection with the operation of thework-holder, This fluid motor comprises a cylinder 34, one end of whichis secured to the inner surface of the rear wall 35 of the verticalsupport or slide ll. A piston 36 (Fig. 8) on the inner end of a pistonrod 31 operates within the cylinder 34, while the outer end of thepiston rod 31 is connected to a vertically extending arm 38 secured tothe upper portion of the tool-holder or slide 2|. Fluid under pressureis admitted in successive charges to either end of the cylinder 34whereby the slide 28 is moved step-by-step in either direction in ahorizontal plane at right angles to the direction of travel of theworkholder 4.

The direction in which the intermittent movements of the tool-holder orslide 28 are made is under the control of a piston type reversing valveindicated at 34' (Fig. 8), and when a desired number of movements ismade in one direction, the valve is longitudinally shifted to change themovement to the reverse direction. This valve is contained in a valvehousing integrally attached to the tool-holder fluid motor cylinder 34,Fig. 8, and may be manually shifted by means of the forwardly extendingstem extension 26 ending in a knob 26' outside the forward wall of thevertical support 3|. In the automatic operation of the machine, thevalve is shifted by the tool-holder stroke limiting dogs Ill! and I05,the dog I09, which limits the rearward movement being shown in Figs. 1,2 and 8, while the dog I09 which limits the forward motion of thetool-holder is shown in plan in Fig. 8. It is identical with the dog I09except that it is in reversed-hand form.

These dogs I09 and I09 are adjustably secured to a T-slot bar I09"attached to the tool-holder or slide 28, and effect the reversal of thetoolholder reverse valve through linkage which consists of a rock-shaftI ill rotatably mounted in the vertical support'3l, a down-turned leverarm H0 on the outer end of the rock shaft H0 in such position as toproject in the path of the dogs I09 and Hill whereby the shaft isrocked, and an up-turned, forked lever Ill, Figs. 2 and 8, whichstraddles the valve extension 26 between a pair of collars 28" securedto this extension. It should 'be explained that with this type of valvereversing linkage and valve that as the valve passes over center, allfluid pressure that created the movement of the tool-holder or slide iscut oil; that is, each dog can move or shift a valve of this type buthalf its reversing stroke only, To complete the stroke, use is made of awedge-cam and an over-the-center spring arrangement whereby theremaining portion of the reversing stroke is brought about by the actionor a spring. The wedge-cam is secured to the valve extension 2', Figs. 2and-8, and is indicated at H2, and the spring at H2 (Fig. 8) containedin a housing attached to the cylinder 34. The spring acts through aplunger I II on one side or the other of the wedge-cam H2, whereby thevalve is shifted in a manner well known to those acquainted with thisart.

Fluid is conveyed to the'cylinder 34 by means of conduit 38, the fluidbeing admitted to the cylinder through ports 4| and 42 respectively, inthe forward and rear ends of the cylinder heads of the cylinder 34 underthe control of hydraulic valve control mechanism in a manner later to bedescribed.

The grinding wheel spindle 25 is rotated by means of an electric motorshown conventionally in Fig. 1, 44 representing the field ring and 45representing the rotor of this motor, the rotor being secured directlyto the spindle.

The fluid under pressure is supplied to the hydraulic valve controlmechanism by means of a pump 46 driven by a small electric motor (notshown). A conduit 48 connected to the suction side of the pump 46conveys fluid from a receptacle 49, the suction end of the conduit 48being submerged below the fluid level of the fluid which is stored inthe receptacle. To the discharge side of the pump is connected a pipeill which leads to the valve control mechanism [3; interposed in thispipe is a pressure regulating and relief device shown conventionally at5| whereby the pressure is regulated.

Valve control mechanism The manner in which the work-holder 4 isstarted, stopped, automatically reversed at the ends of the desiredstroke follows a customary practice. The supply of fluid to either endof the work-holder fluid motor is under the direct control of a masterpiston valve which itself is under the control of the previouslymentioned pilot valve 23 (center, Fig. 8). It is preferable to interposea stopping, starting and throttling valve 58 between the source ofsupply of the fluid and the work-holder fluid motor whereby themovements and rate of speed of the work-holder may be controlledindependently of the movement of the pilot valve. The advantages of thisconstruction are that the operator may stop the work-holder at any pointdesired and resume operations in either direction at the same or changedrate of speed. The pilot valve 23 also controls the successiveintermittent movements of the tool-head whereby when the work-holdermovement is stopped no movement of the toolhead may be made except by aseparate control means, there being a distinct advantage in thisprovision, as in case if the stopping of the workholder is for thepurpose of making measurements on the work, continued motion of thetoolhead at this time might be a source of danger to the operator. Themaster valve is given a reciprocatory movement so as to supply fluid toone end and allow the exhaust of the fluid from the other end of thework-holder fluid motor.

Referring to Fig. 8, center portion, the master valve is indicated at53. It consists of a series of lands or piston portions integrallyattached to a cylindrical rod and is closely fitted in a comparativelylong bore 51 in the lower portion of the hydraulic valve control bodyl3. Fluid is fed to the throttle valve 58 from a port 55, thencedownwardly through a port 55' which leads directly into the bore 51. Thestop and throttle valve 58 of the plug type is horizontally positionedin the valve body ll, intersecting the port 55', whereby the fluid maybe entirely cut of! and prevented from reaching the master valve 53. Alever 94 is attached to the cylindrical extension of the throttle valve58 by which this valve is actuated.

Referring to Fig. 8, in the plug type valve 58 a suitable notch 59 ismachined in one side of the valve body in alignment with the port 55' sothat when the throttle valve 88 is rotated, in the present case througha one-quarter turn, the full capacity or the port it is presented for aflow or fluid to the master valve bore 51.

as a free piston, and is provided at its central portion with the landBl (Fig. 8). In this view the land Bil is in position to permit a flowof fluid from the port II to the conduit l2 leading to the left-hand endof the work-holder motor cylinder 5 with the obvious result that theworkholder will move to the right. As the workholder moves in thisdirection, the right end of the cylinder is opened to exhaust byproviding that the flow of fluid is reversed through the conduit ii andis discharged to the storage tank 49 through a port 82 which will benoticed leading directly from the master valve bore into a cored exhaustpassage 83 which is positioned in parallel relation to the master valvebore 51. Fluid from the exhaust port it is eventually returned through aconduit N, then through a mechanically operated hydraulic deviceindicated in general at 253 (right central portion, Fig. 8) designed toreduce work-holder speed as this member is approaching the loadingposition during the automatic grinding cycle, then through a conduit IIto the tank 48. A description of the retarding device appears later.

The position of the master valve as shown in Fig. 8 is a result of fluidpressure existing at this time in the extreme left end of the mastervalve bore 51. This pressure acts against the land ll of the mastervalve and therefore moves the valve to the right end of the bore. Thefluid which caused the movement is supplied under the control of thepilot valve in the following manner: Fluid pressure from the port I58enters the pilot valve bore 85 between, at this time, the centralenlarged land Ill and left-hand land I! of the pilot valve. Two portslead from this portion of the bore; the function of one of these ports69' being explained hereafter. The other port I2 leads to the left endof the master valve bore 51, while at ll is shown an exhaust port, atpresent blocked by the land II. The fluid flows into the downwardlypositioned port 12 into the master valve bore 51 to move the mastervalve 53 to the right.

So long as the master valve is in this position, fluid will flow intothe left end of the workholder fluid motor cylinder 5 and cause theworkholder to move to the right. When the dog I on the work-holderstrikes the lug IS, the resulting pivotal movement of the reversinglever ll moves the pilot valve to the left and as the pilot valvecontrols the master valve, the master valve is moved to the right, whichmovement reverses the work-holder movement. The manner in which themaster valve is moved to the left is identical with that alreadydescribed for the master valve movement to the right. In Fig. 8 thepilot valve is at its extreme right hand position, this being the resultof a previous workholder reversal. 0n the movement of the pilot valve tothe left, fluid pressure is diverted from the port 56 to a pair of ports81 and 88. One of these ports 81 corresponds to the port 68' at the leftend of the pilot valve bore, its purpose appearing later. The other portBl leads downwardly and fluid flowing therethrough flows through anexternal conduit 243 and eventually arrives at the extreme right end ofthe master valve bore but in so doing the fluid passes through anelectro-hydraulic blocking device 89 (right center, Fig. 8) to bedescribed fully later, and from the blocking device 88 through a secondexternal conduit 2 to the right end of the master valve bore 51.Simultaneously, with the downward flow just described, the fluid at theextreme left end of the master valve bore displaced by the movement ofthe master valve is flowing to exhaust in reverse flow through the port12 into the pilot valve bore. With the pilot valve at its left positionas seen in the figure, the ports 68' and I! are in communication withthe exhaust port II which leads to the exhaust conduit 84.

Continued movement of the work-holder l to the left follows until thedog I! strikes the lug ll of the work-holder reverse lever is. Thisrestores the pilot valve 23 to the right-hand position as seen in Fig.8, with the results described. This movement also connects the extremeright end of the master valve bore to exhaust, permitting fluidtherefrom to flow in reverse order through the conduit 24!, the blockingdevice 89, conduit 2, and port 88 into the pilot valve bore 66 andthence through the downwardly extending port Bi which communicates withthe previously mentioned exhaust port Bi, and thence to the main exhaustconduit 84.

Tool-holder motor The motor which operates the toolholder receives aregulated quantity of fluid at each reversal of the work-holder'and issupplied with fluid from the same source as the work-holder motor. Thisis accomplished by providing an admission valve for the tool-holdermotor which is operated by the fluid and at a speed in proportion to thepressure of the fluid so that upon a lower pressure a longer timeinterval is allowed to admit the fluid to the tool-holder motor, whileat a greater pressure of the fluid a shorter time interval is allowed toadmit the fluid to the toolholder motor, thus insuring the admission ofa substantially uniform quantity of fluid to the tool-holder motor uponeach reversal of the work-holder.

The fluid necessary to move the tool-holder is taken from the commonsupply, i. e., from the port 58 in the valve body l3, and is deliveredto the tool-holder fluid motor cylinder after passing a manuallyoperated tool-holder throttle valve I01 and a fluid-operated admissionvalve III, which like the master valve 53 is in the nature of afree-piston.

The throttle valve iill is manually adjusted by means of the hand leverI01 to govern the extent of the intermittent movements by regulating theamount of fluid supplied to the tool holder cylinder 3|, while the valveI02 controls the timing of the tool-holder intermittent movements.

The valve N32 is a cylindrical reciprocating valve closely fltted in ahorizontal bore ifll (Fig. 8) which intersects a port llil which conveysfluid from the port 56. The port MI is normally closed by either one ofthe solid portions of the valve I02, and thereby prevents movement ofthe tool-holder during grinding operations except at the ends of thework-holder strokes when the grinding wheel is clear of the work.

The reciprocatory movement of the valve I02 is merely a longitudinalshifting in its bore IIII under the impulse of fluid pressure admittedalternately to the ends of the bore Ill, conveyed thereto. on the onehand, from the port 80, and on the other, from the port ll. Thereforethe right end of the valve ill! is exposed to pressure conveyed from theright end of the pilot valve bore 68, while the left end is acted uponby fluid conveyed from the left end of the pilot valve bore Ii. so thatas the pilot valve is shifted at workholder reversals, so also is thevalve I02 given a single movement from-one end to the other of itsstroke for each movement of the pilot valve.

It was stated that the port IIII is normally closed by the valve I02. Toallow admission of fluid through this port Ill whereby the toolholder ismoved at the proper time, the valve II! is provided at its centralportion with a fluid supply opening in the nature of a narrowcircumierential groove Ilil. During the space of time that the grooveIIM is passing the ends of the port III, a charge of fluid is permittedto pass through the port III, and after the valve passes to the oppositeend of the bore Ill3, this port IflI is again closed by one of the solidportions of the valve. The quantity of fluid so admitted is smallbecause it is necessary only to overcome the friction oi the tool-holderand to force a similar small quantity from the opposite side of thetoolholder motor piston. For this reason, the groove I" is narrow, andthe valve I02 admits only the fluid that is able to pass therethroughduring the short space of time that elapses while the groove Ill ispassing the port IIII.

In Fig. Bthe position of the tool-holder reversing valve II is such thatthe intermittent movement of the toolholder is being made rearwardly orto the left in the view, inasmuch as fluid pressure being delivered tothe valve chamber from the supply conduit 39 is diverted by the valve isinto the port ll leading to the forward end 01' the cylinder 34. Fluiddisplaced from the opposite and flows in reverse through the port 42again into the valve chamber, thence into an open port 40' incommunication with the toolholder exhaust conduit 40.

When the tool-holder is to be reversed so that the intermittentmovements are to be made in a forward direction or to the right in theview, the reversing valve is longitudinally shifted forwardly either bycontact of the Stroke-limiting dog I" with the rock-shaft lever or bymanual means, whereby the fluid pressure is directed by the new positionof the valve into the rear or left end of the cylinder ll by way of theport I, while the path for fluid-displaced from the forward end of thecylinder at this time is seen to be through the port II and into theexhaust conduit I. through the short port Iii". It is obvious that oneor the other of the companion ports ll or ill" will be closed by thereversing valve 34 according to the position of the valve.

In the operation of the machine constructed according to the descriptionjust given which corresponds to that of the patent mentioned, thegrinding wheel is preferably placed near an edge of the work-piece, andis fed intermittently across the work as the work-table is reciprocated.

When the grinding wheel has removed all of the stock at this elevationof the wheel, the wheel is lowered manually. When the work-piece isfinished and removed, the operator manually elevates the grinding wheelfor a start on the next piece.

Automatic control devices By the improvements to be nowdescribcd, it isprovided that at each reversal of the tool-holder;

yet of the work-holder reciprocations or the accompanylng traversingintermittent movements of the tool-holder.

One purp se of allowing the machine to continue to run withoutdown-feeding oi the toolsupport is to provide a smoothing or finishingoperation on the work-piece which automatically follow the down-feedingperiod. The smoothing operation may be known as the spark-out time,since evidence is given by lack of sparks from the grinding wheel thatthe smoothing operation is completed. The length of time the finishingor smoothing operation is allowed to continue is variable at will, andit is further provided in the improved machine that at the conclusion ofthe spark-out time, the work-holder is caused automatically to move to aloading position. The loading position is usually located at a far pointon the base at some distance from the grinding wheel in order to furtherinsure the safety of the operator, and after the work-holder comes to astop, the tool-support is automatically elevated to a precisepredetermined height.

Mechanical features of automatic down-feed and elevation fortool-support The description that follows relates to the devices whichare added to the machine constructed according to the specifications setout in the patent mentioned whereby the present improved machine isobtained.

It was previously mentioned that a housing containing certain devicespertaining to the new construction was located on the forward wall ofthe base I. This housing is indicated at I. The housing has a centralopening through which the cross-shaft 22 of the tool-support elevatingmechanism projects, on the outer end of which shaft the elevationhand-wheel 22' is secured.

On the portion of the cross-shaft I! (Fig. 2) within the housing III issecured a pair of ratchet wheels I" and I", with which pawls cooperate.In the present instance, two pawls oflset in relation to each other areused for each ratchet wheel, the pawls I45 and Ill (Figs. 5, 6 and 7)cooperating with the ratchet wheel I, while the pawls I" and I coactwith the ratchet wheel I. flhe pawls I" and I" are pivotally connectedwith a pawl arm I, known as the down-feed pawl arm, rctata'bly carriedon the hub I50 of the ratchet wheel I, while the pawls I" and I" aresimilarly pivotally connected with a pawl arm Iii, called the elevatingpawl arm, rotatably supported on the hub I82 of the ratchet wheel I.Since the pawls are located below their respective ratchet wheels, it ispreferable that the pawls are spring-pressed into engagement with theratchet wheels, compression springs such as are indicated at I" beingemployed for the purpose.

The ratchet wheels and therefore the crossshaft are alternately givenpartial rotation by hydraulic fluid motors, liquid pressure such as oilbeing preferred for, among other reasons, an inherent smoothness ofaction. The valves for these fluid motors are electrically controlledand actuated as will be brought out in the description, use being madeof certain now available accurately performing switches. It will also bemade clear that but one of the ratchet wheels is actuated at a time, andthat each returns to a normal position wherein no interference to manualoperation can be offered.

To transmit the motion of the fluid motors to 78 the elevating mechanismthe lower end of each pawl arm is provided with a. segment of gearteeth. Referring to the down-feed pawl arm I49 the gear tooth segmentalportion is shown at I54, meshing with which is a hydraulic piston I55 inthe upper portion of which rack teeth I55 are out. In itsinitial stageof manufacture the piston I55 is a cylindrical rod having the rack teethmachined in its upper surface as explained. As such, the pistoncomprises a portion 01' a fluid motor, the cylinder for which is locatedin the lower portion of the housing I40 and is indicated at I51,asbestseen inFigs. 5, 6 and 8.

The elevation; pawl arm I5I-ls also provided with a segment of gearteeth as shown at I58, meshing with which teeth is a second rack pistonII! of another fluid motor located in the housing I. The cylinder boreof this second fluid. motor is indicated at Ill and as seen in Figs. 5and 6 is located in a parallel position with reference to the fluidmotor I51.

The hydraulic pressure by which the fluid motors perform theirrespective functions is derived from the main fluid pressure systemthrough a conduit Iii, Fig. 8, being branched oil the main conduit IIIleading from the relief valve 5|. conduit III further branches forming apair of conduits, one, at I62 carrying fluid pressure to a control valveindicated in general at I53, while the second of these branches I84leads to a second control valve also indicated in general at I65.

In Fig. '1 it is seen that the rack pistons I55 and I5! are disposed inparallel relation with each other; as are also the rack arms and ratchetwheels; however, in Fig. 8 these parts are, placed side by side in orderto more clearly show their functions.

The purpose of the control valves is to control the flow of fluidpressure to and from the downfeeding and elevating fluid motors. Themovable parts of the valves are actuated by electrical means and thefore part of the following descrip tion will deal first with themechanical and hydraulic features pertaining to these valves, the :18eption of the electrical portions being made Referring to the controlvalve indicated at I", the movable part thereof consists of a pistontype valve I" which has enlarged lands or spools at each end and anarrower land at the. central portion.

The conduit 18! delivers fluid pressure to the central portion oi thebore I61 in which the movable valve Ili is fitted, and as seen in Fig.8. the piston valve I is positioned in the left end of its bore, wherebyany fluid pressure entering passes to the right of the central land to aport I" in the opposite side of the bore. This port I" communicates bymeans of the conduit I69 with the right end of the bore I51 of thedownfeedlng fluid motor containing the rack piston valve I55, the fluidreaching this end by passing through the internal passage I590 in thehousing I48 (Figs. 5 and 8). This position of the control valve I55 ismaintained ,as a normal position, the valve being returned and retainedthere by a compression spring I10 located at the right end of the pistonvalve. By this position of the piston valve, the rack piston 155 is heldat the left end of its travel, which position is the normal position 01the rack piston.

The control valve 185 is identical with the valve Just described. Itspiston valve, indicated at "I, is maintained at the right end of itsbore as a normal position by the compression spring I12, in whichposition fluid pressure flows to the left of The* the central landthrough the conduit I13 and internal port I15a in the housing I" (Figs.7 and 8) to the left end of the second, or elevating fluid motorcontaining the rack piston I59 and at this normal position of the pistonvalve ill the rack piston is retained in the right end of its bore asits normal position.

The purpose of causing the control valves and rack pistons to return tothese normal positions as described is to permit when desired of themanual handling of the machine at which time the tool-support may beelevated or lowered manually, whereby it is possible to change over froma machine which is operated in every respect as was the machine asdescribed in the patent mentioned to the automatic machine of thepresent application with no more than the mere closing of an electricswitch.

In order to permit manual elevation and lower- I ing of thetool-support, the pawls connected with the pawl arms are disengaged fromcontact with the ratchetwheels. The means for causing this disengagementis the use of curved pawl-withdrawing shields encompassing a part of thelower portion of the ratchet wheels. Referring to the first of theseshields, there is one seen at I14 (Figs. 5, 6, 7 and 8) secured to a lugI15 on the interior wall of the housing I". The shield is cut away asshown at I18 (Fig. 7) to accommodate the oflset pawls, but each of thepair 01' pawls I45 and I48 is disengaged at the same time which occurswhen the rack piston returns to its normal position.

The other shield is shown at I11 in Fig. '1. This shield is secured tothe lug I18 similar to the lug I15 and the shield covers a portion ofthe ratchet wheel I44, whereby on the return movement of the pawl armI5] due to the return of the control valve "I to its normal positionwithdraws the pawls I41 and I48 out of engagement with the elevatingratchet wheel 141. Like the shield I14, the shield I11 is cut away atI11 whereby each pawl I41 and I48 leaves the ratchet wheel I44 at thesame time.

Electrical features of down-feed of tool-support The parts justdescribed constitute the mechanical and hydraulic lowering and elevatingmeans, the actuation of which is dependent on electric switchingarrangements such as will now be described.

It will be observed that the diilerence between the ratchet wheels I45and I44 is merely that the ratchet teeth point in opposite directions,thus, with an angular partial rotation of the pawl arm I43 from itsnormal position as seen in Fig. 5, the pawls I45 and I46 will slip oilthe shield I14 into engagement with the ratchet teeth and turn thatwheel I43 in an anti-clock-wise direction. It will be understood thatsince the elevating ratchet wheel I44 is also keyed to the cross-shaft Ithat this ratchet wheel also at this time turns in an anti-clock-wisedirection, but with no eilect since the pawls I41 and I48 are kept fromcontact with the ratchet wheel I 44 by riding on their shield.

In the present machine, clock-wise rotation of the hand wheel I42,whether by manual or autotro-hydraulic means, the rack piston I55 ismoved to the right, importing a partial rotation to the rack arm I49 inan anti-clock-wise direction.

The automatic elevation, the control for which will be fully describedlater, is eilected by a movement of the rack piston I", which causes thepawls H1 and ill to slip oil the disengaging shield II'I to engage theteeth of the ratchet wheel I to impart to this. ratchet wheel a partialrotation in a clock-wise direction.

As before stated, the control valve I83 controls the movement of therack piston I". The means for actuating the control valve itselfconsists of electrical equipment including a solenoid to move the valve.a time relay to provide a variable time lapse and a switch to energizethe time relay and with it, the solenoid.

The automatic down-feeding movement of the tool-support is timed tooccur when a complete traverse of the grinding wheel across theworkpiece has been made, and before the grinding wheel starts on thefollowing traversing movement. The shifting of the tool-holder reversingvalve ll when the reverse of the tool-holder is made provides a meansfor bringing about the energization oi. the electrical portions oi thedown-feed arrangements.

In that part of Fig. 8 in which electrical circuits are shown, thecircuits consist of suitable pilot current and power current circuits.The pilot The following down-feed is due to occur at the next followingtool-holder reversal, during which event the cam will approach, actuateand pass by the switch. It will likely, also, be evident, however, thatmomentary closing of the switch III will provide an energization of thesolenoid ill of such short time duration that the hydraulic mem bers oithe down-feed arrangement will have insufficient time in which to carryout the functions circuits are shown in light lines, while the heavierlines indicate power circuits. The power circuits are preferablyemployed incarrying current to and from the electro-magnets to bedescribed.

On the valve stem extension 26 of the toolholder reversing valve llthere is secured a cam ill which closes a switch llil during thereversing reciprocations of the tool-holder valve. The switch "I is asingle-pole, single-throw switch and as seen is only momentarily closed,the movable member of which is a spring arm so that the switch opensimmediately after the passage of the cam I" thereby, and with the rod asshown. the switch I" is actuated for each movement of the valve 34'whether the valve is moved forwardly 0r rearwardly.

The closing of the switch ill results in a flow of pilot currentindirectly to a down-feed electromagnet in the form in the present caseof a solenoid ill (lower left portion, Fig. 8) the movable armature ofwhich is connected to an outer extension of the down-feed control valveI", whereby the energization of this solenoid results in a shift of thevalve I to the right. This movement then results in a flow of fluidpressure to the left end of the down-feed rack piston I" to bring abouta down-feed of the tool-support ll, as described.

The movement of the valve I" by reason of the energization of thesolenoid III is made against the compression of the valve return springill, therefore, when the solenoid III is deenergized, the spring I'llreturns the valve and the connected solenoid armature to the normalposition agithe left end of the cylinder of the valve body flow to thedown-feed rack piston I" and causes it to move to its normal position atthe left end of its travel. As before mentioned, at this position thepawls "I and I" are disengaged from the ratchet wheel I, so that if theoperator should desire, he may manually operate the elevation mechanismwithout interference by the pawls.

In explanation of the statement tha the downfeed switch III is closedonly momentarily, it should be made clear that the reason for thisfeature is that in order to be effective for the next followingdown-feed in automatic cycle grinding operations, the switch should benormally open.

This return of the valve reverses the fluid I for which they areintended. Consequently an electrical timer relay device is interposedbetween the down-feed switch I" and the solenoid I" such thatwiilprolong the energization of the solenoid Iii for a suitably long periodof time.

Before the description of the timer relay is made, an explanation ofanother switch which acts in conjunction with the down-feed switch itswill be brought in. The switch in question acts to terminate thedown-feeding portion of the automatic grinding cycle, and further startsthe machine on that portion of the cycle previously mentioned as thesmoothing or spark-out operation.

0n the vertical slide Ii which carries the toolholder there is securedan adjustable dog having a means for obtaining the precise adjustment inkeeping with the accuracy of which the machine is capable. The dog(Figs. 4 and 8) consists of a body II! which is secured to a T -slot bari which in turn is secured to the vertical slide if,

by the use of which T-slot bar the dog is readily adjustable so as tosuit different working conditions. For the more precise adjustmentsmentioned, there is secured to the T-slot bar I above the dog I" ananchor block I". The switch contacting dog I82 and the anchor block IIIare connected together by a screw I86 preferably of a micrometer type,the screw being provided with a comparatively fine thread and graduatedindic'ia on an enlargement of the screw. By loosening the T-bolts I" andill. both dog and anchor block may be shifted to any position on theT-slot bar Ill as a unit, while the precise adjustment may be made bytightening the anchor block and moving the contacting dog ill by meansof the micrometer screw.

The contacting dog I82 operates the movable element I89, Fig. 8, of asingle-pole, double-throw switch I mounted on the column 33, Figs. 1. 2and 4. The movable member I89 is springpressed so as to be maintainednormally closed against the stationary contact "I: that is, the

7 right side of this single-pole double throw switch is normally closed.As the vertical support 3! descends during the down-feeding portion ofthe automatic cycle, the contacting dog eventually makes contact-with acam lever ll! pivotally mounted on a bracket ill secured to the columnI! in such positionthat a plunger ill transmits the motion received fromthe dog I82 to the movable switch member I89. Should the verticalsupport or slide ll be lowered, as during manual operation. of themachine, below the cam lever I82. the contacting portion of the dog it!will lift and rotate partially the cam lever when the slide is againelevated, the lever returning by gravity to its normal position as seenin the diagram.

side of the switch I90 are in series, which allows that the tool-supportwill be intermittently lowered and the grinding wheel will remove stockfrom the work-piece, so long as the dog I82 is apart from the cam leverI92, for at each reversal of the tool-holder pilot current will flow tothe down-feed switch I from the still closed right side of the switch Ithen through the conductor 200 to the timer relay indicated in generalat 20I (Fig. 8 only).

The timer relay is so-called since on application of current to it bythe closing of a momentarily operated switch as is the case here, itsrelay switch 209 may be maintained in an opened or closed condition asdesired for a variable length of time, though the electrical impulsethat caused the actuation of the relay switch has been cut oil by theopening of the switch I80. The means for providing the delay is on theorder of a dashpot in which there is fitted a piston, the piston rod orwhich actuates the relay switch.

The dash-pot cylinder is indicated at 202, the piston at 209 and thepreferably non-ferrous piston rod at 204. The piston is normallyretained in the lower portion of the cylinder by a compression spring205, a. boss 208 on the lower side of the piston acting as a stop toimit the downward movement 01' the piston. To raise the piston 203 bythe closing of the down-feed switch I00, the pilot current flows fromthe conductor 200 through an electro-magnet in the form in the presentcase of a solenoid coil 201 surrounding the piston rod, a portion 208 ofwhich rod is I or magnetic material such as iron serving as an armaturewhereby the magnetism set up by this energization of the coil willattract the armature to lift the piston 202. Although this coil 201 isknown as a holding coil when speaking of relays in general, it should beunderstood that its energization is momentary only, and that the coildoes not holdthe movable parts of the relay. The return of pilot currentto the supply switch I is through the conductor 201'.

The upward movement of the piston and other movable parts occurssuddenly on the single momentary impulse delivered to the coil 201 bythe closure of the down-feed switch I00, which as explained beforeimmediately opens and the coil is also immediately de-energilted. Butthe energization is sufllcient to cause elevation oi the movable membersof the relay which then start to descend. As soon as the upstroke is theswitch by reason of the greater "strength of the dash-pot spring 205.

The upward movement of the piston carries the arm 2I2 to an elevation asshown in broken lines which is somewhat above the point were the movablemember 2 of the switch will stop when it makes contact with thestationary part 2Il oi the switch, a limit for the upward movement beingprovided in the form of a boss on the upper side of the dash-pot piston202.

It was stated that the upward movement of the piston and connectedmovable parts of the relay was made suddenly. It will be explained thata rapidly made upward movement is not essential to the proper operationof this timer relay, but is only incidental. The time lapse is measuredfrom the time the relay switch 289 is alowed to close by relieving thepressure of the arm 2 I 2 on the switch to the time when the switch isagain opened by the descending arm and to provide the time lapse, thedescent is made at a relatively slow rate as desired. As is usual withdash-pot arrangements, one stroke may be made at a rapid rate, while theother may be made at a slower rate. In the present case, displacement ofsome medium such as air at an adjustable relatively slower rate providesfor the slower descent.

On the up-stroke, the air displaced from the upper portion of thedash-pot cylinder 282 flows to the lower part of the cylinder, where atthis time suction is occurring. Two passages are provided for thetransfer of this displaced air, one passage being shown on the rightside of the dashpot cylinder through an externally positioned non-returncheck valve 2, and another e shown at the left side of the cylinder asindicated at 2l5. The check valve offers little resistance to thedownward flow of the displaced air, but prevents return therethrough,whereby such air must return to the upper portion of the cylinder on thedown-stroke of the piston through the passage 2I5. To impart a. desiredvariable descent rate. a needle valve M8 is interposed in the passage2I5, whereby the flow of diwlaced air started a relay switch 209previously mentioned as receiving pilot current from the conductor I91is allowed to close. This relay switch 209 is a single-pole, singlethrowswitch, and although it would ordinarily be classed as a normally closedswitch in view of the action of the spring 2I0 on the movable member 2"of the is subject to the restriction offered by the manner in which theneedle valve is adjusted.

The closing of the relay switch 209 on the upward stroke of the relayparts allows Pilot current to flow through a conductor 2" to anelectro-magnet in the form of a Power contactor 2|. (lower central partof Fig. 8) adapted. to handle the heavier power current taken from thepower main 2I9 leading from the power current switch 220 (upper rightportion, Fig. 8). The return of pilot current from the contactor 2I8 isshown at 22I, this conductor leading to the pilot current supply switchI95.

The energization of the power oontactor 2I8 permits power current toflow through a conductor 222 to the previously mentioned solenoid "I(left lower portion, Fig. 8) a conductor 220 forming the other part ofthis circuit and bei in connection with the power main switch 228.

Energization oi the solenoid III, which may be termed the down-feedsolenoid, brings about a lowering or down-feed of the tool-support asmentioned before, inasmuch as the down teed control valve I88 is shiftedand fluid pressure then flows to the left end of the down-feedrack-piston I55 through the conduit I89 and internal port I89b causingan anti-clockwise partial rotation of the ratchet wheel Ill.

It can be seen that momentary energization only of the down-feedsolenoid III, as would be a'avacos the case had the simple switch I beenemployed without the added timer relay, the operation of the valvemoving solenoid I8I would have been interfered with, likely to theextent that the pawls would not move so far as to engage the teeth oftheir ratchet wheel. With the timer relay, however, a suflicient timelapse is given to insure that the down-teed mechanism may make its fullintended stroke of whatever length desired within the capacity of themechanism, and during this time, the machine is continuing in itsautomatic grinding cycle.

While the timer relay 20I is maintaining energization of the down-feedsolenoid III, the control valve I86 is being retained at the right end01 its stroke against the compression of the valve spring I10. It isevident that the valve must be returned to its normal position beforeanother down-feed stroke can be made, consequently the solenoid must betie-energized. This is brought about when the timer relay arm 2I2descends sufllciently to open the relay switch 209, and the needle valve2I6 may be so set as to allow the opening of this relay switch 2I I assoon as it is certain that the down-feed rack piston I55 has made itsfull intended stroke. In practice, the time lapse is of less than a.minute in duration, being measured rather in seconds than otherwise. 7

Following the opening of the relay switch 2| I, de-energization of thedown-feed solenoid occurs, the valve spring I10 forces the control valveI65 to the left to thereby return the rack piston I55 to the left,withdrawing the pawls from engagement with the down-feed ratchet wheelI43.

The distance the tool-support may be automatically lowered is variable,the adjustment for which is provided by a screw 225, Figs. 5 and 6. Asseen in these figures in connection with Fig. 7, the screw 225 ispositioned in the path of the rack arm I49 whereby the angular stroke ofthis member may be varied from a full stroke as offered by the fulltravel of the rack piston I55 to the right, in which event the screw isbacked out sufilciently to permit this full stroke, to a partial stroke,such as is shown in Fig. 6, wherein the screw 225 is shown turned in tostop the rack arm I49 before the full stroke is made. It will beunderstood that the down-feed stroke, whatever the adjusted length maybe, is always made from the normal position of the rack arm and pistonI55 at the left of its travel as seen in Fig. 5 wherein the pawls areshown disengaged from the ratchet wheel.

When the tool support SI has been automatioally lowered thepredetermined distance (upper right portion, Fig. 8) the dog I02 on thesupport makes contact with and actuates the cam lever I92 to break thecircuit that controls the downi'eed devices for the support by movingthe movable contact member IIQ of the switch I90 out. of contact withthe member IBI.

Smoothing out 0! work The cam lever by its movement also shifts themovable member I00 of the switch I00 in contact with the stationarymember 226 of the switch I00 and thereby closes anothercircuit wherebyanother sequence in the automatic grinding cycle is started. this beingthe smoothing or "sparkout" operation previously referred to. Thisis llw d by the automatic return of the workholder to the loading position,and the elevation of the vertical slide to the proper height for a.start for automatic grinding on the next workpiece.

The closing of the left side of switch I starts a second timer relay 229which controls, the movements of the work-holder to loading position andthe elevation 01' the tool support and also by reason of a slow closingthereof allows for a smoothing out period. This relay 220 is of slightlydifferent construction from the timer relay 20I since it is not employedfor the purpose of permitting a time lapse during which a fluid motormay make a stroke, but to provide a variable time period for thesmoothing or spark-out time before the reciprocation of the work-holderis ended and the work-holder moved to load position. v

When the left side of the switch I90 is closed, pilot current flowsthrough a conductor 226' to the electromagnet in the term in the presentcase of a solenoid coil 22! of the second timer relay (center rightportion, Fig. 8 only) indicated in general at 220 to be known as thesmoothing or spark-out timer relay. The energization of this collresults in the elevation of a rod 230 having an armature portion 220'which further results in the relatively sudden lowering of the forkedleft side 23I of a pivoted doublearmed rocking lever 202, to which therod is pivotally connected. This movement of the lever 232 isaccomplished against the tension of the spring 200, so that when thecoil 220 is deenergired, the lever and armature are returned to theirnormal position as seen in Fig. 8.

Through the use of the spring 223 in so retaining the lever 232, thepiston rod 220 and piston 235 of this timer relay 220 are held in theirnormal upper position in the relay against the compression of the spring228, this spring being preterably relatively weak as compared to thelever spring 200. At the upper end of the piston rod is a laterallyprojecting arm 231 in position to make contact with the relay switchindicated in general at 238. This switch has a movable, springoperatedcontact element 230 having a projecting extended end positioned so as tobe depressed by the arm 23] when the same is lowered by the spring 238on energization of the solenoid coil 220.

The descent of the movable portions of this timer relay, by which ismeant the piston and piston rod, is made at a suitabLv slow rate suchthat will provide the desired time for the smoothing or spark-outoperation. The duration of time allowed for the spark-out operation isthat time taken up during the downward approach of the arm 201 towardthe relay switch 230, and when the arm makes contact with the movableswitch member 239 and forces this member in contact with the stationaryelement of the relay switch 230 to close this switch, this closing marksthe end of the spark-out time, following which the work-holder will beremoved to the loading position.

Portions oi the timer relay Just described are much like those describedin connection with the explanation of the first mentioned down-feedtimer relay "I, the similarity being in the manner in which thedisplaced air is metered in its flow from opposite ends of the dash-potcylinder. The regulation of the rate of descent is eiiected by theadjustment or a needle valve 200 which is employed to suitably restrictthe iiow or air from the lower to the upper end of the cylinder 2. Anon-return check valve 202 is employed to allow tree flow of displacedair from the upper to the lower end of the cylinder and to prevent areverse flow therethrough, forcing the displaced air to pass by theneedle valve 2". The same comment as to it not being essential that thetimer relay should move at a rapid rate on its idle stroke made inconnection with the description of the down-feed timer relay 2" appliesto this second timer relay 228.

Before going into the explanation of what follows when the relay switch23! of the spark-out timer relay 22! is closed, it will be explainedthat the spark-out timer coil 228 remains energized during the spark-outtime in order to delay the opening of the contacts of this relay, since,to properly carry out the smoothing or spark-out operation, it isnecessary that the grinding wheel remain at the desired low point itreached when the left side of the double-throw switch I was closed. Itwill be further evident that during the spark-out operation, nodown-feeding is to be made, and such is not made, although the down-feedswitch I" is being repeatedly closed at each reversal of the tool-holdertraversing movements; but, since the right side of the double-throwswitch I" which is in series with the down-feed switch I was opened whenthe grinding wheel reached the adjusted depth, no further down-feedingis possible because the circuit which controls the power relay 2|! isnow broken.

Return of work-holder to loading position At the conclusion of thespark-out operation which occurs whenthe spark-out relay switch 238 isclosed, reciprocation of the work-holder is arrested and the work-holderis automatically returned to the loading position, a portion of whichreturn stroke is made at a reduced rate of movement and also the toolsupport II is elevated to the upper starting point.

In reference to the description of the manner in which the work-holderis returned tc the loading position it will be pointed out that in theroutine grinding operation, whether after the manner as described inconnection with a machine constructed according to the patent mentionedor according to the design of the present application, that the range ofreciprotions of the work-holder is normally confined to a portion of themachine by the spacing of the work-holder reversing dogs I and I5. Tomove the work-holder automatically to a portion of the base that may beoutside the normal grinding stroke as set by these dogs means that oneof the reversing dogs must be rendered temporarily ineflective to causea work-holder reverse]. Of several methods that may be available, thefollowing is preferred as it lends itself to automatic operation of themachine and does not involve a readjustmentof one of the reversirig dogsfor this purpose.

In the present case, the loading position is at the right hand end ofthe base of the machine, and this means that the left hand dog II is theone which is to be made ineffective to allow the work-holder to move tothe loading position. It is this dog It which indirectly will cause ashifting of the master valve 53 when the workholder is moving toward theright and the dog strikes and rocks the reverse lever It, but, to allowthe work-holder to moveon by the point where it would ordinarily bereversed, the master valve is not shifted although the pilot valve 23 isshifted as usual.

By the devices to be described the master valve 53 is not shifted by theleft hand dog ll at this time because the fluid pressure under controlof the pilot valve 23 which ordinarily would bring about a shift is nowtemporarily blocked from reaching the master valve. The blocking meanswas previously referred to in connection with explaining the manner inwhich the master valve 53 is shifted under the normal control or thepilot valve 23, where it was stated that fluid pressure flowing throughthe passage 88 eventually to arrive at the right hand end of the mastervalve bore is conveyed externally through the external conduit 243 incommunication with the port 88 to the blocking device indicated at I!(right central portion, Fig. 8) and from this device through the conduit245 to the right end of th master valve bore.

The blocking device 89 is in the present case a solenoid operatedhydraulic valve, the solenoid being indicated at 246. The movable partis in the form of a grooved piston valve connected to the solenoid, thevalve being springreturned in order that it and the armature oi thesolenoid may be restored to the normal position when the solenoid isdeenergized. The

valve is shown at 241, the groove mentioned being indicated at 248,while the spring is seen at 249. The effect of the spring is to maintainthe valve normally so that the circumferential groove 2 is in registrywith the port openings in communication with the external conduits 243and 5 whereby a free flow of fluid pressure is permitted to pass to theright end of the master valve except at the time when the workholder isto be moved to the loading position.

As stated, this movement is under the control of th spark-out timerrelay switch 238 which in turn is controlled by switch I90. When thisswitch 238 is closed as dscribed at the end of the grinding andsmoothing or spark-out operations, pilot current taken from a.continuation of the conductor I91 flows through a conductor III whichleads to and energizes a power contactor relay 250 (lower right portion,Fig. 8), which in turn allows power current taken from the the powermain conductor 2i! through a conductor 2! to energize the blocking valvesolenoid 246, the return flow conductor for the pilot current beingshown at 250, and for the power current at 252. The effect of energizingthe blocking solenoid 24B'is to depress the valve 2" to place thecircumferential groove out of registry whereby the fluid pressure flowfrom the pilot valve is blocked. This obviously prevents a movement ofthe master valve such as ordinarily occurs when the pilot valve 23 isshifted and therefore the work-holder continues on its stroke to theright and moves to the loading position at the right.

It should be explained that the dogs II and I! are offset with relationto one another as are likewise the lugs l5 and I1 so that the lug IIwill stand in the path of the dog 04 and the lug ll will stand in thepath of the dog l5. When the work-holder is moved to loading positionthe dog it striking the lug l6 will throw the lever to the right and thedog will then ride over the lug as the work-holder moves to its loadingposition. Upon the return movement of the work table the dog M will rideover the lug l8 and pass at one side of the lug i1 and the dog II willride at one side of the. lug ii and strike the lug I! to again shift thepilot valve.

In the explanation of the method by which the master valve movement wasblocked by the energization of the blocking solenoid 248, it must alsobe brought out how this solenoid is dee ergized, mention of this partthe explanation being made at this point in order to make it clear that,while this blocking solenoid is energized by the closing of the switch238, the opening of this same switch does not bring aboutde-energization of the solenoid 246, this being the function of anotherswitch 254 which is manually actuated by the operator in re-starting theautomatic cycle.

It will be remembered that with the master valve 53 in its right handposition as seen in Fig. 8, as long as the blocking solenoid isenergized, the work-holder willcontinue to move toward the right untilit stops at the loading position, which may be when the work-holderreaches the end of the base or the end of the cylinder of thework-holder fluid motor where it will be retained by reason of fluidpressure on the left side of the piston. It is also clear that shouldthe blocking solenoid 248 be deenergized, the work-holder wouldimmediately reverse itself and move to the left, the pilot valve 23having already been shifted. It is one of the purposes of thisconstruction to provide that the workholder be moved to the loadingposition and to be retained in that position for as long as the operatormay desire. It is a further purpose that the tool-support 3| beautomatically elevated when the work-holder reached the loadingposition, which elevation will open the left side of the double-throwswitch I90. This in turn will cause deenergization oi the spark-outtimer relay solenoid coil 22B whereby the Spring 233 will cause theopening of the relay switch 238, with deenergization of the blockingsolenoid 246 and,

it not prevented, consequent immediate re-start of the work-holder.Obviously, this is not desirable inasmuch as the operator should haveample time in which to re-load the machine. Before the explanation ismade of the manner in which the solenoid 245 is controlled jointly bytwo separate switches, a description will be made of the means wherebythe speed of the work-holder is reduced as it approaches the loadingposition.

Speed retarding device for work-holder when moved to loading positionThe retarding device is a valve arrangement interposed in thework-holder fluid motor exhaust conduit. The device is indicated at 282(right center, Fig. 8) and contains a grooved, spring-pressed pistonvalve 254 similar to the blocking valve 241. In the normal position ofthe retarding piston valve 254 as effected by the vlave spring 256, afree flow of exhaust fluid is aflorded by the registry oi thecircumferential groove 25'! with ports in the cylinder wall which are incommunication with the exhaust conduits l4 and '4'. It can be seen thatdepression of the retarding valve willreduce proportionately the speedof the work-holder. To bring about this speed reduction, a retarding cam258 (left center, Fig. 8) is attached to the T-slot of the work-holder,in the present case, between the pair 01' work-holder reverse dogs l4and IS.

The lower portion of the cam is formed with an oflset to pass thereverse lever II. When the work-holder moves sufliciently far toward theright, the lower upwardly sloping cam surface 2" makes contact 'with theretarding valve 254, this valve having an upward extension projectingthrough the upper portion of the valve cylinder 2. To provide that thedepth to which the retarding valve is depressed may be adlustablyregulated, the valve stem extension is fitted with a threaded tappetscrew 280. As seen in the right central portion 01' Fig. 8, theretarding cam is shown in dot-dash lines in position to make contactwith the tappet screw 260 to depress the valve stem and its valve 254whereby the groove may be somewhat out of registry with the ports. Areduced flow will thereby be permitted, it not being the intention tocut oil entirely the flow of exhaust fluid.

The work-holder will continue to move at the reduced rate of speedtoward the right, the retarding valve now being held at the desireddepth or the horizontal under portion 258' or the cam 258 until thework-holder abuts against a stop, which may be of any nature, such aswhen the piston 6 of the work-holder fluid motor I reaches the rightcylinder head of this fluid motor. This is a dead stop, and as wasmentioned previously, the work-holder will be retained at this point byfluid pressure. It may be noted that with this method it is notnecessary to alter the work-holdor speed control throttle 58, wherebythe operator is further relieved of some responsibility in thisconnection.

At about the same time that the work-holder reaches the actual stop orloading position, a switch 262 (right central portion, Fig. 8) which maybe known as the slide elevation switch, is closed by the upper portion283 of the retarding earn 258. The slide elevating switch is a normallyopen switch and is in series with it normally closed manually operatedswitch 264 to be referred to later, known as the re-start switch. Pilotcurrent is taken from a continuation of the conductor I81 on closing ofthe tool-support elevation switch 282 and passed through the restartswitch 264 which is a normally closed switch, and through a conductor288 to the coil 266 of an interlocking relay 261 (right central portion,Fig. 8). From this coil 266, the pilot current is returned to theconductor 22| leading to the pilot current supply switch I85.

One purpose of this interlocking relay 2" is to provide that theenergization of the blocking solenoid 246 which was initiated by theclosing of the left side of the double-throw switch Ill and which causedthe movement of the work-holder to the loading position, is maintainedby the interlocking relay, because as was explained, as soon aselevation of the tool-support II is permitted, the accompanying openingof the left side of the double-throw switch I would, without the use orthe interlocking relay, have caused the deenergization of both thespark-out timer relay and the blocking valve solenoids 228 and 248, withthe consequent immediate re-start of the work-holder, To put there-starting under the manual control of the operator is the function ofthe interlocking relay.

When the coil 26! of the interlocking relay 261 is energized by theclosing of the switch 242, two circuits are, established. One is a pilotcurrent circuit that take over the energization of the blocking valvesolenoid 246. Pilot current from the conductor IN is delivered to one orthe contacts of the interlocking relay 261, and from a companion contactpoint of this relay through a short (in this showing) conductor 24! to aJunction with the previously mentioned conductor 218' leading to thepower relay 2". Therefore, regardless of the position or the left side01' the double-throw switch I or the spark-out relay switch 228, theblocking valve will be retalned in position to maintain the work-holderin the loading position.

Tool elevating device The other circuit closed by the elevation of theinterlocking relay 261 is a power circuit whereby the tool support 3| iselevated. Power current is taken from the power main 2|! through aconductor 210 to the interlocking relay 281 and from this relay througha power conductor ill to an electro-magnet in the form, in the presentcase, of a solenoid 112, to be known as the tool-support elevationelectro-magnet, which is connected with the previously referred to pilotcontrol valve Hi. When the elevation solenoid 212 is energized the valveIll is moved to the left, whereby a flow of fluid pressure through theconduit l1! to the port illb at the right end of the slide elevatingrack piston I" is permitted, so that as this rack piston moves to theleft the pawls H1 and H8 ride of! of the pawl shield ill (Fig. andengage the ratchet wheel i to thereby elevate the tool-support llthrough the medium of the shaft 22, pinion 2|, gear 2! and screw 20. Therack piston I" remains at the left position until a manual operation ofthe switch 264 is made which will be explained later.

The elevation of the tool-support II is accomplished in a singlemovement in contrast with the successive, comparatively smalldown-feed,- ing movements, and the amount of elevation. is the sum ofthe down-feeding movements, therefore, the tool-support is returned tothe same height as before. Inasmuch as the total amount of down-feedingis variable by the manner in which the down-feeding limiting dog I" isadjusted with respect to the double-throw switch I", the amount ofelevation should be made equal to the total down-feed movement. This isprovided for by the use of a stroke limiting screw I'll similar to theadjusting screw 22! by which, as explained before, the stroke of thedown-feed pawl arm I is determined. The elevation limiting screw 213 isbest seen in Fig. 5 at the left side of this view. It shouldbe madeclear that the angular stroke allowed the downfeed pawl arm I" by themanner in which the stroke limiting screw 225 is adjusted does notaffect the total down-feed amount; the position of the screw 225 merelyprovides that the total amount of down-feed is broken up into a numberof comparatively small, successive down-feed movements.

Deeneroization of spark-out timer relay The automatic elevation of thetool-support obviously opens the left side of the double-throw switch Iwhereby the coil 22! of the spark-out timer relay is deenergized. Thereturn spring III of this relay acts to restore the movable parts of therelay to the normal position, opening the relay switch 238. Displacementof air during the upward movement of the parts is made freely throughthe check-valve 242, and it will be clear as mentioned in the similarcase of the downfeed relay, that it is not essential that a rapidup-stroke of these relay parts is made.

Return of blocking valve of work-holder motor to normal position Openingof the relay switch 238 does not, however. cause deenergization of theblocking device solenoid 2", but it will be evident that if either ofthe switches 28! or 254 is opened, that the interlocking relay 266 willbe deenergized since these switches are in series with each other andwith the coil 22! of the interlocking relay 281.

The urpose of the re-start switch I is then clear, for when the operatordesires to again start the machine, it is necessary only to open thisswitch 264. By this openingthe coil 2 of the interlocking relay isdeenergized and the two described circuits that were closed when therelay was energized are now broken. The deenergization of the blockingvalve solenoid 246 is one result, as the relay 2" which supplies powercurrent thereto will be deenergized, following which the blocking valveis forced upwardly by the action of its return spring 2", whereby theflow of fluid pressure from the already shifted pilot valve 23 that hadbeen restrained is now allowed. by the registry of the groove 2 with theports. to continue in its flow to the right end of the master valve 53.The resulting shift of the master valve 53 admits fluid pressure to theright end of the work-holder fluid motor I to start the work-holder tothe left. The movement will be comparatively slow at first until theretarding cam 258 is moved off the retarding valve 255 whereupon thespeed of movement of the work-holder is accelerated to its formergrindin rate.

Deenerglzation of tool-holder elevation solenoid The other circuit thatis interrupted by the manual opening of the re-start switch I resultsin'the deenergization of the elevating solenoid 212, as a. consequenceof which the elevation control valve ill connected therewith is returnedto its normal position toward the right by the action of its spring I12.The elevating rack-piston then also moves to the right to its normalposition, since the control valve I'll is returned to the right by thespring I12, and fluid pressure is admitted to the left end of theelevating rack-piston to swing pawl arm Iii anticlock-wise. therebywithdrawing the pawls I" and I from engagement with the elevatingratchet wheel I. As might be inferred, the return to normal position ofthe automatic hydraulic elevating devices may be allowed to take placewhile the automatic grinding cycle is again in progress. Fluid that isexhausted from the elevating control valve I65 and from the downfeedvalveiii as well is returned to the main exhaust fluid conduit 64' bymeans of the manifold ili'.

Although a dresser or wheel truing device is not shown in the presentapplication, it is evident that it will be found necessary from time totime to true the grinding wheel. Compensation for the reduction ingrinding wheel diameter by truing is had by manually lowering thetool-support ill a suitable amount. If the manual lowering is in thesame amount as half the reduction of wheel diameter by truing, thelowermost portion of the grinding wheel periphery, the grinding contactsurface, is again at the same elevation with respect to the surface ofthe workholder. However, without a certain slight readjustment of thedescent limiting dog III, the next work-piece to be finished in theautomatic cycle would be left too thick by the amount dressed off oneside of the wheel. To compensate for this possible error, the dog in isadjusted upwardly a distance qual to the distance the tool-support waslowered manually. It so happens that at times the amount removed bytruing or natural wear is comparatively slight, perhaps merely .001" or.002", whereby thepurpose of the micrometer screw I" is clear. since aprecise adjustment of the dog is possible. It will be understood thatthe anchor block I99 is not loosened for this adjustment.

It will be explained that the machine as constructed and operated inpractice is capable of such accuracy in repetition that with work-piecesof comparatively uniform thickness, that it is not necessary to make anyalteration to the tool-support position as regards elevation, from theposition in which it was left at the last movement of the work-holderwhen the latter was moving to the loading position. That is, theposition of the grinding wheel as regards its relation with the forwardor rear edge or center of the work-piece may have been at random whenthe work-holder moved to the loading position. If the re-loading of anew work-piece is not made inconvenient by this random position of thegrinding wheel, there is no need to alter its position and the nextgrinding cycle may start at once on the new work-piece. However, if theoperator desires, he may so adjust the control devices, particularlyreferring here to the needle valve 249 of the spark-out timer relay soas to prolong or make shorter, as he desires, the time allowed for thesmoothing or spark-out operation whereby the closing of the relay switch299 is timed to occur when, say, the grinding wheel is nearly or isfully retracted.

It should now be clear that the grinding machine of this application issimilar in general design to the machine of the patent mentioned andthat the devices by which the automatic grinding operations are carriedout as described are to be considered as additional elements madeauxiliary to the design of the machine of that patent. By the addedelements, a grinding machine is made possible, the operation of which issufllciently automatic in character as to permit that comparativelylarge volume of acceptable work is turned out by operators of relativelylimited experience.

Further, if it is desired to operate the improved machine of the presentapplication according to the principles as set out in the patent, it isnecessary only to open the pilot current supply and power current supplyswitches. In so doing, all the electrical circuits shown in thediagrammatic Fig. 8 are for the time being taken out of service and theseveral compression or tension springs function to retain the controlvalves or like members in their respective normal positions. Thisstatement more particularly relates to the springs I19 and I12controlling the down-feed and elevating valves I69 and HI whereby thepawls are retained disengaged from the ratchet wheels.

Operation of devices Down-feed of tool-supporL-With the workholder andtool-holder reciprocating and toolsupport at its uppermost position, thetool-support is fed by step-by-step toward the work as follows: Thecontacts I99 and HI of the switch I99 being normally closed, pilotcurrent is fed to the switch I99 so that at each reciprocation of thevalve stem 26 of the tool-holder reversing valve 94' pilot current willbe fed through the 2i and screw 29 lowers the tool-support 9| one stepto the extent allowed by the adjusting screw 213. The relay 29I delaysdeenergization of the solenoid I9I to allow the mechanical devices timeto operate. The step-by-step feed continues until the dog I92 on thetool-support contacts the cam lever I92 which through the stem I94throws the movable contact member I99 of the switch I99 to the leftwhich breaks the pilot circuit I99 to the switch I99 so that no furthercurrent will be supplied to the time relay 2M and therefore no furthercurrent supplied to the power relay 2I9, whereby the solenoid I9l willcease to function and the down-feed of the tool-support will bearrested.

Smoothing out of work peri0d.-The next operation is to smooth out thework before the workholder has ceased to reciprocate and is moved toloading position. Time is allowed, therefore, for the smoothing outoperation by delayin the automatic return to loading position of theworkholder and also for the elevation of the tool-support as follows:When the dog I92 breaks the contacts I99 and HI, it moves the contactI99 to close with contact 229 so that pilot current will flow throughthe circuit 229 to the solenoid coil 228 of the time relay 229, thisbeing a relay in the pilot circuit which delays flow of pilot current tothe power rela 299 through circuit I91 and 299 which when closed permitspower current to flow to the solenoid 248 which operates the valve 2" toblock supply of fluid to one end of the cylinder of the fluid motor thatreciprocates the work-holder. The contacts of this relay 229 are slowlyclosed and before closing the smoothing out operation is permitted.

Return of work-holder to loading position.- When the contacts I99 and229 of the switch I99 are closed, solenoid coil 229 of relay 229 isenergized through circuit 226' and the contacts of relay 229 are closedby delayed action thereof sufficient to allow the smoothing outoperation. Pilot current then flows to the power relay 299 through theconductor 299' to close the power circuit to the solenoid 299 to movethe valve 241 to block fluid supply to one end of the workholderreciprocating fluid motor to allow the motor to move the work-holder toloading position. When the work-holder moves to loading position itcloses the switch 292 and allows pilot current to flow through theconductor 299 to the coil 296 of an interlocking relay 291. When thecontacts of the relay 261 are closed pilot current will then be suppliedto the power relay 299 through the circuit I91, contacts of relay 291,and circuits 299 and 299' to maintain the blocking valve in blockingposition to allow time for placing a new workpiece on the work-holder,this condition prevailing until the manually operated switch 294 isopened by the operator; one purpose of the interlocking relay 291 beingto maintain the power relay 269 energized when the contacts of the timerelay 229 are opened by the breaking of the circuit 229', which followsso soon as the interlocking relay 261 is energized, for the closing ofthe relay 261 also closes a power circuit which elevates thetool-support 9|, permitting the breaking of the contacts I99 and 229 ofthe switch I99 and hence the breaking of the pilot circuit 229'.

Elevation of tool-holder.-When the interlocking relay 291 is closed inthe manner described a powercircuit is established through the solenoid212 to operate the valve III to permit fluid to flow to the right end ofthe cylinder I99 to move the rack pinion I99 to the left so as toModification of tool support feeding mechanism In Figs. 9 to 13 there isillustrated a modification of the electrical devices which arecontrolled by the tool-support feeding mechanism. Instead of having thedog I82 located on the tool slide ll in this modification the dog,indicated at I82, is secured to the periphery of the handwheel 22" by aset-screw 300. The dog in this, case carries a fixed pin 80! having abeveled upper portion which is adapted to contact, at the end of thedown feed of the slide 3|. with the rounded end of a stem 30!. I'hisstem is adjustably mounted in a rocking lever 303, having an extension303' which is journalled upon a pin 304 carried by two cars 305 whichare secured to a bracket 306 carried by the housing I40. The lever isnormally supported for automatic operation in a horizontal plane by aboss 303" thereon (Fig. 11) which rests against the bracket 306. Thestem 302 is part of a micrometer and is screwthreaded in a bushing 301secured in the rocking lever 303, the threads between the bushin and thestem being of a rather coarse character. On the outer left hand end ofthis bushing there is rotatably mounted a micrometer type thimble 308,having the customary graduation such as the ones marked 1 2 7 8 9 whichcooperate with the co-axial scribe Y in the upper surface of the bushing301. The end of the stem fits in a central aperture in the thimble andis pinned to the thimble so that by turning the thlmble on the bushingthe stem may be adjusted with relation to the beveled pin 30!. In orderto provide triction so that endwise or axial pressure on this rathercoarse pitch mike-screw stem when the dog I82 contacts therewith so thatthe screw stem will not be backed off, the right-hand end of the bushingis provided with an auxiliary tapered bushing 301'. One side of thisauxiliary bushing is split as shown in Fig. 11, whereby as the auxiliarybushing is forced into the bushing 301 it closes in on the stem toi'rictionally hold it but not to an extent as to preclude its adjustmentby rotation of the thimble.

The extension 303 of the rocking lever 803,

carries a pin 309 secured therein in any suitable manner and is adaptedto cooperate with a plunger ill associated with a switch whichcorresponds to the switch I" previously described. The switch, indicatedat ill is a panel mounted switch supported in the interior of thebracket 3", the wiring of this switch being the same as that previouslydescribed and as shown in Fig. 13, the reference characters in Fig. 13being the same with the addition of the exponent a.

In operation, when the feeding devices for the tool support are operatedin the manner before described the hand wheel 22" naturally moves withthem so that when the beveled upper side of the pin lllll strikes therounded end of the stem 30! that end of the lever 303 which carries thestem is rocked upwardly to the position shown by the dot-dash lines 303ain Fig. 11 sufficiently to press the switch plunger 3"! in to operatethe switch. Further movement of the parts, and it is practically thesame movement, brings the end of the dog I82 against the end of the stem30! to positively arrest further movement of the hand wheel (Fig. 12)and hence arrest any further movement of the downward feeding movementof the tool slide II. If the machine is to be operated otherwise than asan automatic down-feed grinder the lever Ill! is swung to the dot-dashposition indicated at "Sb (Fig. 11) which removes the rocking lever 303out of the path of the dog I81.

One of the advantages is that a positive stop is provided, by reason ofthe contact of the dog I82 with pin Jill.

Another advantage is that when the grinding wheel must be loweredfurther as a result of reduction in wheel diameter by wheel wear andtrulng it is convenient to provide this further lowering by backing oilthe rounded-end stern 302. (See Fig. 10 in the sectional part.)

The indicia forms a convenient means for properly adjusting the stemwith relation to the dog to contact the limit of the down-feed of thetoolsupport.

Upon the closing of the switch contacts lila and 2260. by the rocking ofthe lever 30! the spark-out period follows as described in connectionwith the description of the other form. When the spark-out time iscompleted, the operation follows the previously described method; thatis, the work-table moves to the loading position where it is retaineduntil the re-start manually-operated switch 284 is opened; in suchmovement, the work-table closes the switch It! to thereby causeautomatic elevation of the toolholder. The opening of the re-startswitch 2" causes the return of the work-table to the working position.Such elevation obviously imparts a partial rotation oi the hand wheel22" in a clock-wise direction (the down-feeding direction beingantl-clock-wise) which carries the dog I82 away from the rocking lever308, allowing this lever to be lowered to its normal position occupiedduring automatic operation as seen in full lines in Fig. 11. By thisoperation the sparkout side of the double-throw switch I as representedby the contacts 228a and "9a is opened, and the same movement of thecontact "9a closing by contact with the contact iflla that side of theswitch I!!! which is in series with the down-feed switch lfllla soautomatic down-feeding may be resumed.

Having thus described my invention, I claim:

1. In a grinding machine, a reciprocatory work-holder, a travelingtool-supporting device, a tool carried by said device, means for feedingsaid tool-supporting device toward the work on said work-holder, fluidmotor-operated means for reciprocating said work-holder, andelectricallyoperated means automatically retarding the actuatlon of saidmotor-operated means in one di rection of the reciprocation of saidwork-holder, an electrical control circuit therefor, a circuit make andbreak device in said circuit operated by the travel of thetool-supporting device as it approaches the limit of its range ofmovement in one direction while the work-holder continues to be moved bysaid motor-operated means at reduced speed to a loading position beyondits normal range of reciprocation and .a. delayed action relay in saidcircuit for temporarily maintaining said electrically operated means inits operative condition subsequent to initiation oi return movement ofthe traveling tool-support.

2. In a grinding machine, a reciprocatory work-holder, a travelingtool-supporting device. a tool carried by said device, means for feedingsaid tool-supporting device toward the'work on said work-holder, fluidmotoroperated means for asvaaoa reciprocating said work-holdercomprising a cylinder, a fluid-operated piston therein, a fluidcirculatory conduit communicating with the cylinder, an electricallyoperated cut-oil valve in the fluid circulatory conduit for reducing thecirculation of fluid relative to the cylinder of said fluid motor toretard the operation of said motor operated means in one direction ofthe reciprocation of said work-holder, while the work-holder continuesto be moved by said motor operated means to a loading position beyondits range of reciprocation an electrical control circuit for saidcut-oil valve, a circuit break and make device therein operated by thetravel movement of the tool-supporting device, and a timer membergoverning the return to normal of the cut-oil valve when operatedindependently of the further travel of the tool supporting device.

3. In a grinding machine, a reciprocatory work-holder, a travelingtool-supporting device, a tool carried by said device, means for feedingsaid tool-supporting device toward the work on said work-rholder, fluidmotor-operated means for reciprocating said work-holder,electrically-operated means for retarding the actuation of saidmotor-operated means in one direction of the reciprocation of saidwork-holder while the workholder continues to be moved by saidmotor-operated means to a loading position beyond its normal range ofreciprocation, an electrical control circuit therefor, a make and breakdevice in the circuit operated by the travel motion of thetoolsupporting device, and releasable controlled electrical meansoperated by said work-holder for maintaining said electrically operatedmeans efl'ective to retain said work-holder in loading position aftercontrol of said circuit has been removed from the influence of saidtool-supporting device.

4. In a grinding machine, a reciprocatory work-holder, a travelingtool-supporting device, a tool carried by said tool-supporting device,electrically controlled fluid actuating means for feeding said devicetoward the work on said workholder, means for reciprocating saidwork-holder comprising a fluid motor, and electrically oper ated meanscontrolled by said electrically controlled fluid actuating means forfeeding said tool-supporting device for preventing reversal of thereciprocatory work-holder by operation of said fluid motor whereby thefluid motor causes the work-holder to continue to move to loadingposition comprising a blocking valve to block fluid supply to one end ofsaid fluid motor, an electromagnet connected with said valve, means forenergizing said magnet actuated by said electrically controlled fluidactuating means for feed ing said tool-supporting device after the endof its operation upon the work including a delayed action relay, andmanually controlled electrical switch devices closed by said work-holderwhen,

moved to loading position ,for maintaining said magnet energized toretain said work-holder in loading position after the energizationthereof has been removed from the control of said toolsupportlng device.

5. In a grinding machine, an adjustable tool support, a reciprocal toolsupported thereby, a reciprocatory work-holder, means to impart afeeding movement to said tool-support with relation to said work-holder,means including a fluid motor for reciprocating said work-holder,electrically operated means including an electromagnet for blocking thesupply of fluid to one end of the cylinder of said motor to permit saidwork-holder to be moved to loading position thereby, a first switchclosed by said means to impart a feeding movement to said tool-supportat the end of the grinding operation of said tool upon the work. anelectrically controlled retractive mechanism energized by the approachof the tool support to the limit of its range of travel for restoringsaid tool-support to initial position to permit opening of said flrstswitch, a second switch energized by the closing of said flrst switch,including means to delay the closin thereof to permit a smoothingoperation of the tool and adapted to be closed to supply current to saidmagnet when said first switch is closed, a third switch in series withthe second switch, closed by said work-support when moved to its loadingposition, a fourth switch closed upon the closing of said third switchto maintain said magnet energized after said first and second switcheshave been opened by the restoring movement of said tool-support, and afifth switch in series with said fourth switch manually operabletodeenergize said magnet to permit said blocking means to return tonormal position.

6. In a grinding machine, a reciprocatory work-holder, a fluid operatedmotor to reciprocate said holder, automatic reversing means for themotor operable by the work-holder as it approaches the limit of aprescribed range of movement in each direction under influence of fluidpressure supplied alternately to opposite ends of the motor, anelectrical circuit including an electrically operated device fortemporarily arresting the supply of fluid under pressure to one end ofthe motor while fluid pressure continues to be supplied to the oppositeend thereof to continue the operation of the motor and movement of thework-holder in one direction beyond its normal range of reciprocatorymovement into a loading position, regardless of the operation of thereversiris, means, thereby, an adjustable tool-supporting device, meansto cause a relative traversing movement between said holder and device,electrically controlled means actuated by said traversing means to feedsaid tool-supporting device toward t e work on said work-holder,electrically controiled means actuated by said electrically-controlledmeans which feed said tool-supporting device to arrest thefeedingmovement of said tooi-supporting device, and electrically controlledactuning means controlled by said work-holder when moved to loadingposition to return said tool-supporting device to initial position,

7. In a grinding machine, a reciprocatory work-holder, an adjustabletool-supportin d vice, a tool carried'by said tool-supporting device,electrically controlled fluid actuating means for feeding said devicetoward the work on said workholder, means for reciprocating saidwork-holder comprisinga fluid motor, and electrically operated meanscontrolled by said tool-supporting device for blocking the reversal ofsaid fluid motor while the work-holder continues to move beyond itsnormal range of reciprocation to loading position comprising a blockingvalve to block fluid supply to one end of said fluid motor while asupply of fluid under pressure is continued to the opposite end thereof,an electromagnet connected with said valve, means for energizing saidmagnet actuated by said tool-supporting device after the end of itsoperation upon the work including a delayed action relay by which themagnet is maintained in energized condition and the blocking valve inoperated position regardless of further movement of the tool supportingdevice,

